Update description of fork schedule.

This updates the description of the config/fork_schedules endpoint to
state that all forks should be returned rather than just the upcoming
forks.

apis/config/fork_schedule.yaml

@@ -1,7 +1,7 @@
 get:
   operationId: getForkSchedule
   summary: Get scheduled upcoming forks.
-  description: Retrieve all scheduled upcoming forks this node is aware of.
+  description: Retrieve all forks, past present and future, of which this node is aware.
   tags:
     - Config
   responses: